Springs, shocks, hardware:
You'll need taller springs and longer shocks. The rear leaf springs should be full packs, not just add-a-leaf.
Longer u-bolts and shims. A proper kit will include these. You'll need bigger bump stops. You may also want to take the opportunity to throw in some par bin eliminators.
You'll need slightly longer lower-control arms.
But you'll get better results in terms of flex and ride comfort if you go with either a long-arm kit, or control arm drop brackets. You need to go over 4" for these two options, though. Adjustable control arms aren't necessary but are beneficial.
When I went from 3" to 5" I installed control arm drop brackets. The ride was extremely harsh at 3", but improved immensely with the drop brackets. It was so awful, if I had to do it again, I would have gone directly to 4.5" of lift. Yeah, it's nice being up higher and having more clearance, but I only did it so I could install drop brackets and get my control arms at an optimum angle.
You'll need longer sway bar links.
You'll want an adjustable track bar (preferably one with a double-shear bracket).
You'll probably want a SYE kit, and a double-cardan driveshaft (cheapest thing to do is get another front driveshaft from a junkyard). This is a good opportunity to install a new chain in the transfer case.
You'll need longer brake lines if you're going to take it offroad. You don't have to get those fancy braided steel lines. For mine, I think I went with YJ brake lines in the rear, and GM brake lines in the front. Maybe it was the other way around, I don't recall.
Probably will need a longer e-brake cable.
Take the opportunity replace bushings all around.
Depending on the leaf springs you go with, your rear shackle angle could be sub-optimal. This can result in a stiff ride in the rear. Shackle relocation brackets can be used to fix this.
Whether you move the center of the tires out with less backspacing or spacers won't make much of a difference. Go with whatever suits you. Neither is going to appreciably wear on the bearings, unless you go with much bigger tires, or combine minimal backspacing and
In my mind, a budget kit is a "booster" lift, which is little more than coil spacers and longer shackles. You can buy used parts from people who have wrecked or upgraded their rigs. You could try to build a "bastard pack" for the rear leaf springs. But my experience is that you have two options for going 3" or higher: 1) upgrade more than just springs and shocks, or 2) regret it.
Also, start soaking every nut and bolt you could possibly need to remove with some sort of penetrating spray. It's also fairly normal to have to cut off bolts, and cut into the frame and floor to deal with broken and weld nuts.
Use the links above, search and read, search and read, and then come back if you still have questions.
In my mind, "doing it right" is a ballpark figure of $2500-3000. Not counting wheels and tires. Others may have managed it for significantly less, I'm not sure.